Effect of Particle Spreading Dynamics on Powder Bed Quality in Metal Additive Manufacturing
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TECHNICAL ARTICLE
Effect of Particle Spreading Dynamics on Powder Bed Quality in Metal Additive Manufacturing Yousub Lee1 · A. Kate Gurnon2 · David Bodner2 · Srdjan Simunovic1 Received: 24 September 2020 / Accepted: 4 November 2020 © This is a U.S. government work and its text is not subject to copyright protection in the United States; however, its text may be subject to foreign copyright protection 2020
Abstract Powder spreading precedes creation of every new layer in powder bed additive manufacturing (AM). The powder spreading process can lead to powder layer defects such as porosity, poor surface roughness and particle segregation. Therefore, the creation of homogeneous layers is the first task for optimal part printing. Discrete element methods (DEM) powder spreading simulations are typically limited to a single layer and/or small number of particles. Therefore, results from such model configurations may not be generalized to multiple layer processes. In this study, a computationally efficient multi-layer powder spreading DEM simulation model is proposed. The model is calibrated experimentally using static Angle of Repose measurements. The adhesion model parameter, cohesive energy density is related to adhesive surface energy and strain energy release rate parameters. The model results show that interaction between particle and the powder spreading rake leads to noticeable variation in packing density, surface roughness, dynamic angle of repose (AOR), particle size distribution, and particle segregation. The powder model is experimentally validated using a recoater spreading rig to measure the dynamic AOR at spreading speeds consistent with recoating speeds and layer heights used in AM processes. Keywords Powder bed additive manufacturing · Powder spreading · Powder bed quality · Multi-layer deposition · Discrete element methods (DEM) · Cohesive energy density
Introduction Metal powder bed additive manufacturing (AM) including laser, electron beam powder bed fusion, and binder jetting has revolutionized the way of designing and manufacturing products [1]. AM provides exceptional design flexibility, which is not achievable in the traditional subtractive manufacturing processes. The AM technologies excel in minimization of machining time, material waste, lead time, shipping time and physical storage space [2]. Powder-based AM processes consist of two key steps of object construction. The first is the powder spreading in which powder is distributed evenly over the entire bed surface including; a previous powder layer or recently * Yousub Lee [email protected] 1
Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
General Electric Global Research, Niskayuna, NY 12309, USA
2
layered part. The second step is the powder fusion or binding wherein the powder particles are melted and solidified by a heat source or bound together by fluidic binders. Most researchers in metal powder bed AM have focused on the melting/solidification stage assuming random or some ide
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